4. Didymium fulvum Sturgis.
- 1917. Didymium fulvum Sturgis, Mycologia, IX., p. 37.
Sporangia gregarious, sessile, elongate or forming curved plasmodiocarps, sometimes confluent, rarely sub-globose, concave beneath, pale-raw-umber in color, 0.5–0.8 mm. in diameter, occasionally seated on a concolorous, membranous, lime-encrusted hypothallus which may form pseudo-stalks; sporangium wall membranous, stained with yellow blotches, thickly sprinkled with clusters of large acicular crystals of pale-yellowish lime; columella very much flattened or obsolete; capillitium an abundant network of delicate, almost straight or flexuose, pale-purple or nearly hyaline threads, frequently with dark, calyciform thickenings as in Mucilago, and occasionally showing fusiform, crystalline blisters; spores dark-purplish-brown, coarsely tuberculate, the tubercles usually arranged in curved lines, paler and smoother on one side, 12.5 to 14.5 µ. Colorado.
5. Didymium crustaceum Fr.
- 1829. Didymium crustaceum Fr., Syst. Myc., III., p. 124.
Sporangia closely aggregated, globose, or by compression deformed, sessile, snow-white, by virtue of the remarkably developed covering of calcareous crystals by which each sporangium is surrounded as if to form a crust, the peridium membranous, colorless, usually shrunken above and depressed; columella pale, small, or obsolete; hypothallus scant or vanishing; capillitium of rather stout violaceous threads seldom branched except at the tips, where they are pale and often bifid, or more than once dichotomously divided; spores strongly warted, globose, violet-brown, 10–13 µ.
This species has in some ways all the outward seeming of a diderma, but cannot be referred to that genus because of the crystalline character of its crust. This is a very marked structure; loosely built up of very large crystals, it is necessarily extremely frail, nevertheless persists, arching over at a considerable distance above the peridium proper. Sometimes, however, caducous, evanescent.
The sporangia are said to be sometimes stipitate. This feature does not appear in any of the material before us. Lister in Mycetozoa Pl. XL., c. draws the capillitium much more delicate than it appears in our specimens. The hypothallus is sometimes noticeable under some of the sporangia where closely crowded, but is not a constant feature.
Rostafinski (by typographical error?) confused in the Monograph, pp. 164, 165, this species with Persoon's Physarum confluens. In the Appendix he substitutes the Friesian nomenclature. Persoon's description of his species is insufficient, and throws no light on the problem whatever.
Rare. Iowa; Black Hills, South Dakota. Reported common in Europe. Canada; Vancouver Island to the St. Lawrence.